The present invention relates to an image qualification method, and more especially to motion detection methods for an optical navigation sensor.
An optical navigation sensor detects motion by comparing image correlations captured at different times. Thus, quality of image can affect motion detection by the optical navigation sensor, and is affected by noise, blurring out of focus, illumination, and other facts. A LED in the optical navigation sensor prevents erroneous detection resulting from variations in illumination. When the optical navigation sensor is exposed to illumination from a fluorescent light driven by 60 Hz or 50 Hz AC power, however, periodical variations result in flicker and subsequent errors in motion detection.
A disadvantage of conventional image qualification is that several image frames are needed to calculate correlations there between to determine whether the optical navigation is in focus. Thus, several buffers are required and time delay is unavoidable.